Drop-mass Technique Research Articles

Exploring the optimal impact force for chronic skeletal muscle injury induced by drop-mass technique in rats.

Introduction: Skeletal muscle injuries are widespread in sports, traffic accidents and natural disasters and some of them with poor prognoses can lead to chronic skeletal muscle damage in the clinic. We induced a chronic skeletal muscle injury by controlling time and contusion force using an acute blunt trauma model that will help us better comprehend the pathological features of chronic skeletal muscle injury. Methods: Several levels of injury were induced by repeatedly striking in 5, 10, and 15 times the gastrocnemius muscle from the same height with 200g weights. After injury, the markers of muscle injury were assessed at 2 and 4 weeks by serum elisa. Electron microscopy, histologic and immunohistochemical staining, and mRNA analysis were used to evaluate the ultrastructure, inflammation, extracellular matrix decomposition, and anabolism of injured muscle in 2 and 4 weeks. Results: All three different kinetic energies can result in skeletal muscle injuries. However, the injured skeletal muscles of rats in each group could not recover within 2 weeks. After 4 weeks, tissue self-repair and reconstruction caused the damage induced by 5J kinetic energy to almost return to normal. In contrast, damage induced by 10J kinetic energy displayed slight improvement compared to that at 2 weeks. Despite this, collagen fibers on the surface of the tissue were disorganized, directionally ambiguous, and intertwined with each other. Myofilaments within the tissue were also arranged disorderly, with blurry and broken Z-lines. Damage caused by 15J kinetic energy was the most severe and displayed no improvements at 4 weeks compared to 2 weeks. At 4 weeks, IL-1β, IL-6, Collagen I, and Collagen III, MMP2 expressions in the 10J group were lower than those at 2 weeks, showing a tendency towards injury stabilization. Conclusion: After 4 weeks of remodeling and repair, the acute skeletal muscle injury model induced by 10J kinetic energy can stabilize pathological manifestations, inflammatory expression, and extracellular matrix synthesis and catabolism, making it an appropriate model for studying chronic skeletal muscle injuries caused by acute injury.

Using complex II as an emerging therapeutic target for the treatment of muscle lesions

After patients has been trapped into skeletal muscle injury, hypoxic and dysfunctional mitochondria brings about a crisis in energy supply that severely disrupts the repair of skeletal muscle. This study aims to elucidate injury-induced adaptations in the mitochondria and provide statistics for the role of complex II in instilling cells with energy under hypoxic conditions. Fifty-six male Wistar rats were divided into control, 12 h, 2 d, 5 d, 7 d, 10 d, 15 d, and 30 d postinjury groups. Contusion injury was made via an instrumented drop-mass technique delivering single impact to the posterior surface of the gastrocnemius of one limb of the rats. ROS levels, loss of mitochondrial membrane potential (MMP), activities of marker enzymes (miCK, LDH, and ALP), and activities of complexes I–III were determined. Our findings reveal that the first 2 d postinjury, especially at 12 h, is the period with most severe oxidative stress. After injury, the activities of mitochondrial complexes I–III display different behaviors based on time and various energy production mechanisms. Our results highlight that complex II participates in electron transport in the acute phase of blunt trauma. We proposed that CII could be a therapeutic target in muscle lesions.

The Effect of Platelet-Rich Plasma on Muscle Contusion Healing in a Rat Model

Background: Current therapy for muscle contusions is usually limited to nonsteroidal anti-inflammatory drugs and/or use of the RICE principle (rest, ice, compression, elevation); thus, other forms of treatment that can potentially accelerate the rate of healing are desirable. Hypotheses: A local injection of platelet-rich plasma (PRP) would lead to accelerated healing rates compared with controls; also, delayed administration of PRP would lead to a blunted response compared with immediate treatment. Study Design: Controlled laboratory study. Methods: Forty-six male Lewis rats each underwent a single blunt, nonpenetrating impact to the gastrocnemius muscle via a drop-mass technique and subsequently received either a single injection of saline into the area of injury immediately after injury (controls, n = 11) or rat PRP (either immediately after injury [PRP day 0, n = 12], the first day after injury [PRP day 1, n = 12], or the third day after injury [PRP day 3, n = 11]). The primary outcome was maximal isometric torque strength of the injured muscle, which was assessed before injury as well as on postinjury days 1, 4, 7, 10, and 14. All animals were sacrificed on postinjury day 15. Histological and immunohistochemical analyses were performed on 6 specimens from each group after sacrifice. Results: The mean platelet concentration in the PRP was 2.19 × 106 (±2.69 × 105)/μL. The mean white blood cell count in the PRP was 22.54 × 103/μL. Each group demonstrated statistically significant decreases in maximal isometric torque strength after injury when compared with preinjury levels, followed by significant increases back toward baseline values by postinjury day 14 (controls, 90.6% ± 7.90%; PRP day 0, 105.0% ± 7.60%; PRP day 1, 92.4% ± 7.60%; PRP day 3, 77.8% ± 7.90%) (P = .121). There were no statistically significant differences between the treatment and control groups at any of the time points. There were also no statistically significant differences between any of the groups in the percentage of centronucleated fibers (controls, 3.31% ± 5.10%; PRP day 0, 0.62% ± 1.59%; PRP day 1, 3.24% ± 5.77%; PRP day 3, 2.13% ± 3.26%) (P = .211) or the presence of inflammatory cells and macrophages. Conclusion: In this rat contusion model, a local injection of PRP into the injured gastrocnemius muscle resulted in no significant differences in functional or histological outcomes, indicating no likely benefit to healing. Additionally, there was no significant difference between immediate or delayed administration of PRP. Clinical Relevance: Before PRP can be recommended for the treatment of muscle contusion injuries, further translational and clinical investigations need to be performed.

Creation of a contusion injury in rabbit skeletal muscle using a drop-mass technique

This study reports our experience in developing a simple, minor injury. After reviewing the literature, a ‘drop-mass’ method was selected where a 201 g, elongated oval-shaped weight was dropped up to 15 times through a 1 m tube onto the left vastus lateralis of New Zealand white rabbits. To determine the extent of injury and degree of healing, biopsies were obtained six days after injury from the healing vastus lateralis of each animal. The tissue was fixed in formal saline, embedded in wax, cut and stained with haematoxylin and eosin (HE) and phosphotungstic acid haematoxylin (PTAH) and examined by light microscopy (LM). The ‘optimal’ injury was created after seven drops, where quite severe, mild and moderately severe trauma was caused to muscle in the juxta-bone, mid and sub-dermal regions respectively. In each region, the muscle exhibited features of healing six days after injury. The ‘drop-mass’ technique appears to cause a contusion within a single muscle of at least three degrees of severity. This previously unreported observation is of particular importance to other researchers wishing to investigate contusion injury in other animal models.

The Time Course Effects of Electroacupuncture on Promoting Skeletal Muscle Regeneration and Inhibiting Excessive Fibrosis after Contusion in Rabbits

The aim of this study was to investigate the longitudinal effects of electroacupuncture (EA) on Zusanli (ST36) and Ashi acupoints in promoting skeletal muscle regeneration and inhibiting excessive fibrosis after contusion in rabbits. Sixty rabbits were randomly divided into four groups: normal, contusion, EA, and recombinant human insulin-like growth factor-I (rhIGF-I). An acute skeletal muscle contusion was produced on the right gastrocnemius (GM) by an instrument-based drop-mass technique. EA was performed for 15 minutes every two days with 0.4 mA (2 Hz), and GM injections were executed with rhIGF-I (0.25 mL once a week). Rabbits treated with EA had a higher T-SOD and T-AOC serum activities and lower MDA serum level, the blood perfusion of which was also significantly higher. In the EA group, the diameter of the myofibril was uniform and the arrangement was regular, contrary to the contusion group. The number and diameter of regenerative myofibers and MHC expression were increased in the EA group. EA treatment significantly decreased fibrosis formation and reduced both GDF-8 and p-Smad2/3 expressions in injured muscle. Our data indicate that EA may promote myofiber regeneration and reduce excessive fibrosis by improving blood flow and antioxidant capacities. Additionally, EA may regulate signaling factor expression after contusion.

Effect of a contusion injury on muscular force, power, work, and fatigue

The purpose of the investigation was to compare alterations in muscular force, power, work, and fatigue following a contusion injury. We hypothesized that power and work would be more greatly reduced than isometric force due to several mechanisms that would alter the force-velocity relationship and impair activation/relaxation kinetics specific to dynamic muscle contractions. Contusion injury was administered to the gastrocnemius muscle of adult rats using the drop-mass technique. Isometric force, power during shortening (10, 25, and 40 mm/s), work produced during cyclic contractions (2 and 4 Hz), and fatigue during 60 work loops, were normalized to dry muscle mass and analyzed in control animals (n=11), as well as 1 h (n=11) and 48 h (n=9) following contusion injury. Passive work increased (30-38%) 48 h after injury compared with control (P<0.01). Isometric force, power, and work were significantly reduced by similar magnitudes 1 h (28-33%) and 48 h (28-38%) after injury compared with control (P<0.01). Fatigue index 1 h post-injury was significantly less than control (75% vs 85%; P=0.02). The observed increases in muscle hysteresis were apparently not large enough to cause greater reductions in power and work than isometric force. We conclude that isometric measures provide adequate quantification of muscular dysfunction following a contusion injury in these animals and may offer sufficient information to determine recovery status in clinical settings as well.

Characteristics of locomotion, muscle strength, and muscle tissue in regenerating rat skeletal muscles

Although numerous studies have aimed to elucidate the mechanisms used to repair the structure and function of injured skeletal muscles, it remains unclear how and when movement recovers following damage. We performed a temporal analysis to characterize the changes in movement, muscle function, and muscle structure after muscle injury induced by the drop-mass technique. At each time-point, movement recovery was determined by ankle kinematic analysis of locomotion, and functional recovery was represented by isometric force. As a histological analysis, the cross-sectional area of myotubes was measured to examine structural regeneration. The dorsiflexion angle of the ankle, as assessed by kinematic analysis of locomotion, increased after injury and then returned to control levels by day 14 post-injury. The isometric force returned to normal levels by day 21 post-injury. However, the size of the myotubes did not reach normal levels, even at day 21 post-injury. These results indicate that recovery of locomotion occurs prior to recovery of isometric force and that functional recovery occurs earlier than structural regeneration. Thus, it is suggested that recovery of the movement and function of injured skeletal muscles might be insufficient as markers for estimating the degree of neuromuscular system reconstitution.

Therapeutic Ultrasound Decreases Mechano-Growth Factor Messenger Ribonucleic Acid Expression After Muscle Contusion Injury

McBrier NM, Lekan JM, Druhan LJ, Devor ST, Merrick MA. Therapeutic ultrasound decreased mechno-growth factor messenger ribonucleic acid expression after muscle contusion injury. Objective To examine the influence of nonthermal ultrasound on mechano-growth factor (MGF) messenger ribonucleic acid (mRNA) expression after blunt trauma. Design A 2×4 factorial multivariate analysis of variance design. Setting University research laboratory. Animals Thirty-six 3- to 4-month-old male Wistar rats (mean weight, 280.8±21.5g). Thirty-two received a bilateral contusion injury to the gastrocnemius via a drop mass technique. Four were control animals. Intervention Ultrasound treatment (frequency, 3MHz; intensity, 0.3W/cm 2; continuous duty cycle) was started 24 hours postinjury and delivered for 5 minutes daily on 4 consecutive days. Treatment was on the left hindlimb and the contralateral right hindlimb was the nonultrasound control. Main Outcome Measures Muscle mass (in grams) and MGF mRNA expression as measured via real-time reverse transcriptase polymerase chain reaction. Results Ultrasound had no effect on muscle mass (F 1,28=2.723, P=.110, 1−β=.357, η 2=.089). Ultrasound treatments decreased MGF mRNA expression in the treated limb compared with the nontreated hindlimb (F 1,28=6.605, P=.016, 1−β=.699, η 2=.191). Conclusions The nonthermal ultrasound treatments resulted in decreased MGF mRNA expression after blunt trauma to the gastrocnemius muscles.

Influence of Post-Injury Ultrasound Treatments on Muscle Specific Insulin-Like Growth Factor (MGF)

Non-thermal ultrasound (US) is commonly used in an attempt to improve skeletal muscle regeneration, although the efficacy of this practice is not firmly established. Researchers have investigated a number of growth factors involved in the activation of satellite cells during the regeneration process, however, muscle-specific insulin-like growth factor (MGF) has not been examined in this context. PURPOSE: To examine the influence of non-thermal ultrasound on markers on MGF following blunt trauma. METHODS: Male Wistar rats received a bilateral contusion injury to superior aspect of the gastrocnemius (GTN) muscle via a drop mass technique. US administration (0.3 W/ cm2, continuous duty cycle) commenced 24-hr post-injury and was delivered 5 minutes daily on 4 consecutive days. Rats received the US treatment on their left hindlimb, and the contralateral right hindlimb served as a non-US control. Dependent variables included muscle mass (g) and MGF mRNA as measured via real time RT PCR. RESULTS: Ultrasound had no effect on muscle mass (F1,28= 2.7, P = 0.11, 1-β = .36, ν = .09). There was a main effect and post-hoc for ultrasound treatments (F1,28= 6.61, P = 0.02, 1-β = .70, ν = .19) and days post-injury (F3,28= 7.3, P = 0.001, 1-β, ν= .44). Ultrasound treatments significantly decreased MGF mRNA levels compared with non-treated hind limb on day 1 (3.5 ± 2.7 vs. 5.8 ± 4.6); day 2 (0.9 ± 0.50 vs. 2.6 ± 2.2); and day 3 (0.7 ± 0.3 vs. 1.6 ± 1.4) post-injury. MGF values on 1 day post-injury were statistically greater than the values observed for days 3 and 4 after injury. CONCLUSIONS: The specific non-thermal ultrasound treatments we studied decreased the mRNA expression of MGF following blunt trauma.

Exercise and Therapeutic Ultrasound in Skeletal Muscle Regeneration

0125 Following skeletal muscle contusion injury, ultrasound (US) is a commonly utilized treatment modality among sports medicine practitioners. There is evidence that the mechanical effects of non-thermal US elicit changes in membrane permeability, which over several days purportedly hastens the post-contusion-injury muscle regenerative process. However, how US influences both satellite cell proliferation and ultimately muscle contractile proteins is poorly understood, and the interaction between US and low-intensity exercise following contusion injury has not been investigated. PURPOSE: To gain enhanced insight into the biological markers underlying the potential rehabilitative process associated with US, and determine if low-intensity exercise (EX) enhances the effect of US treatment. METHODS: Twenty male Wistar rats (8–9 mo) were studied and were randomly assigned to either an EX or NoEX group. Following anesthesia, each rat received a bilateral contusion injury to the gastrocnemius (GTN) muscles. The reproducible injury was generated using a validated drop-mass technique. To visualize satellite cell proliferation, immediately following the contusion injury a pellet of the thymidine analog, bromodeoxyuridine, was implanted subcutaneously in the scruff of the neck. In both groups the right leg received US while the left received no US. The design lead to the generation of 4 groups of 10 GTN muscles: 1) EX + US; 2) EX + NoUS; 3) NoEX + US; and 4) NoEX + NoUS. An additional 5 animals served as a non-injured, − US treated, and− exercised control group. Both exercise and US treatments were administered for four consecutive days, and began 24h post-contusion-injury. Exercise treatment consisted of 20 minutes/day of low-intensity treadmill walking (14m/min), and the US treatments (settings = 0.1 W/cm2 and 3 MHz) were 5 minutes in duration. Left non-US treated legs received sham US treatments. Following all treatment protocols (96h) GTN muscles were surgically removed and rats were sacrificed. GTN muscles were weighed, frozen, and stored at−80°C for analysis of fiber cross-sectional area (CSAf), myofibrillar protein concentration, and satellite cell number. A two way (exercise × treatment) MANOVA was performed. RESULTS: Preliminary results from 5 rats in the NoEx group demonstrate no statistically significant (p<0.05) differences between US-treated and sham-treated muscles in mass (3.25 ± 0.22 g and 3.34 ± 0.23 g, respectively) nor in CSAf (1,600 ± 455.43 square microns and 1,549 ± 1,109.74 square microns, respectively). CONCLUSIONS: The US treatment protocol used appears to have no effect on the measured markers of skeletal muscle regeneration.

Thermal Studies on Energetic Compounds

The nitrate complexes of copper, nickel and zinc with diethylenetriamine (dien) i.e. [Cu(dien)2](NO3)2, [Ni(dien)2](NO3)2·2H2O and [Zn(dien)2](NO3)2 have been prepared and characterised. Thermal studies were undertaken using TG-DTG, DSC, ignition delay (tid) and ignition temperature (IT) measurements. Impact sensitivity was measured using drop mass technique. The kinetic parameters for both non-isothermal and isothermal decomposition of the complexes were evaluated by employing Coats-Redfern (C-R) method and Avrami-Erofeev (A-E) equations (n=2 and 3), respectively. The kinetic analysis, using isothermal TG data, was also made on the basis of model free isoconversional method and plausible mechanistic pathways for their decomposition are proposed. Rapid process was assessed by ignition delay measurements. All these complexes were found to be insensitive towards impact of 2 kg mass hammer up to the height limit (110 cm) of the instrument used. The heat of reaction (?H) for each stage of decomposition was determined using DSC.

Dynamic Surface Tension Measurement with a Dynamic Wilhelmy Plate Technique

An experimental method called dynamic Wilhelmy plate technique (DWPT) for studying dynamic surface tension was designed in this study. A diffusion-controlled model corresponding to the initial and boundary conditions of this method was proposed. Dynamic surface tension of Triton X-100 and SDS was measured with this technique and analyzed with the proposed model. The calculated diffusion coefficients for the short- and long-time approximations are 3.7 × 10−6 and 0.97 × 10−6 cm2/s for Triton X-100 and 4.6 × 10−6 and 0.79 × 10−6 cm2/s for SDS, respectively. The predicted dynamic surface tension with these diffusion coefficients for the simultaneously generated aqueous/air interfaces is in good agreement with the drop mass technique. Another diffusion controlled model that considers the energy barrier at the aqueous/air interface was also proposed in this study. The calculated energy barriers are in the range of 4.1–5.7 RT for Triton X-100 and 6.5–8.0 RT for SDS.

The Effect of Anabolic Steroids and Corticosteroids on Healing of Muscle Contusion Injury

The effect of an anabolic steroid (nandrolone decanoate, 20 mg/kg) and a corticosteroid (methylprednisolone acetate, 25 mg/kg) on healing muscle injured with a drop-mass technique in a reproducible muscle contusion injury model in the rat was studied. Healing was determined by measuring active contractile tension in each muscle and histologic analysis. At day 2, the corticosteroid group showed significant improvement in both twitch and tetanic strength relative to the controls. At day 7, this effect was reversed and the corticosteroid muscles were significantly weaker than the control muscles, but there was still no significant effect seen in the anabolic steroid group. At day 14, the corticosteroid muscles were totally degenerated, with disorganized muscle fiber architecture. The anabolic steroid muscles were significantly stronger in twitch, and a similar trend was seen in tetanus relative to control muscles. The results indicate that in an animal model corticosteroids may be beneficial in the short term, but they cause irreversible damage to healing muscle in the long term, including disordered fiber structure and a marked diminution in force-generating capacity. Anabolic steroids may aid in the healing of muscle contusion injury to speed the recovery of force-generating capacity. Although anabolic steroids are considered renegade drugs, they may have an ethical clinical application to aid healing in severe muscle contusion injury, and their use in the treatment of muscle injuries warrants further research.

Maximal contraction lessens impact response in a muscle contusion model

The effect of muscle contraction on a contusion injury model was studied in the gastrocnemius muscle of anesthetized rats. Both limbs of 18 rats received a contusion injury with a blunt non-penetrating impact. One hind limb was relaxed during impact and the other was electrically stimulated to tetanic contraction. The impact was produced using a drop-mass technique (mass = 171 g, height = 101 cm, spherical radius of impactor tip = 6.4 mm). The impact response was determined by sampling (10 kHz) the transmitted impact force and the displacement of the impactor. In a subgroup of nine rats, the severity of the contusion injury was measured by recording contractile tension in twitch and tetanus within two hours of injury. We found that the peak impact force was significantly less ( p < 0.01), while the peak impact displacement was significantly greater ( p < 0.01) in the contracted limb. Correspondingly, the impact stiffness of the contracted limb was significantly less ( p < 0.01) than the impact stiffness in the relaxed limb. Both impacts produced significant injuries relative to an uninjured control group. The tetanic tension (31 ± 4 N) generated by the muscles that were contracted during impact was significantly ( p < 0.03) greater than that generated by the muscles that were relaxed during impact (27 ± 4 N). The findings from this specific model indicate that the impact response of the limbs with relaxed muscle was dominated by the underlying bone, while maximally contracted muscle decreased the influence of the bone and lessened the impact response. Maximally contracted muscle was not more susceptible to injury and may act as protective mechanism against some impacts.

A muscle contusion injury model. Biomechanics, physiology, and histology.

We developed a reproducible muscle contusion injury and studied its effect on contractile function, histology, and passive failure. An instrumented drop-mass technique (mass, 171 g; height, 102 cm; spherical radius, 6.4 mm) delivered a single impact to the posterior surface of the gastrocnemius muscle in one limb of 40 male Wistar rats. On Day 0, the impact significantly (N = 12, P < 0.01) decreased maximum tetanic tension to 63% of the contralateral control value. Histologic examination demonstrated extravasation of erythrocytes, edema, myofiber disruption, and vacuolation of myofibers. Passive failure initiated at the site of injury. At 2 days, tetanic tension was 75% of controls (N = 11, P < 0.01). Histologically, acute inflammation and phagocytosis were noted. Tetanic tension at 7 days was 81% of controls (N = 8, P < 0.01). Vimentin staining indicated a dramatic increase in myoblast activity. Contractile strength was near normal at 24 days. Histologic examination showed complete regeneration of normal striated muscle fibers. No vimentin activity was found. No passive failures initiated at the injury site. Contusion injury produced a significant deficit in contractile function that continually diminished with gross histologic evidence of degeneration, regeneration, and normalization at the injured muscle fibers.

Dynamic Surface Tension Measurement with the Drop Mass Technique

The minimum surface age of the drop mass technique was extended to the 20 ms range. A new empirical method for calculating the dynamic surface tension from the drop mass uses only the basic forces acting on the drop. The dynamic surface tension results of Triton X100 solutions showed good agreement between two different radius tips and the independent results of other authors. The dynamic surface tension curves of stock sodium dodecyl sulfate and dodecyltrimethylammonium bromide solutions showed the impurity effects predicted and observed by other authors. The addition of a swamping amount of common ion to a dilute dodecyltrimethylammonium bromide solution increased the rate of surface tension reduction and reduced the impurity effect. Micellar solutions of the surfactants exhibited a reduction in the impurity effect.